Boatman told to go for being inattentive (6)
I believe the answer is:
absent
'inattentive' is the definition.
(similar in meaning)
'boatman told to go' is the wordplay.
'boatman' becomes 'ab' (abbreviation for able seaman).
'told to go' becomes 'sent' (sent away).
'ab'+'sent'='ABSENT'
'for being' acts as a link.
(Other definitions for absent that I've seen before include "lack of attention" , "Away" , "Not present - vacuous" , "Missing, lacking" , "Not where one should be" .)